Six-level hybrid extraction/injection scheme terahertz quantum cascade laser with suppressed thermally activated carrier leakage.

This work presents a six-level scheme terahertz (THz) quantum cascade laser (QCL) design in which the resonant-phonon (RP) and the scattering-assisted (SA) injection/extraction are combined within a single AlGaAs/GaAs based structure. By utilizing extra excited states for hybrid extraction/injection channels, this design minimizes the appearance of an intermediate negative differential resistance (NDR) before the lasing threshold. The final negative differential resistance is observed up to 260K and a high characteristic temperature of 259 K is measured.